This application relates to German patent application no. 199 12 265.2, filed Mar. 18, 1999, the disclosure of which is hereby incorporated herein by reference in its entirety.
The present invention relates to a method of providing a constant medicament dose for an inhalational administration at a low inhalation flow rate, as well as to a device appropriate to this end.
The inhalation of medicaments is gaining an ever-increasing importance. In this respect firstly attention must be paid to the fact that aerosol particles efficiently arrive in the lung only wit slow inhalation, i. e. at a low inhalation flow rate. With the so-called powder inhalers so far known, however, comparatively high inhalational flow rates in the range of roughly 60 1/m are required in order to supply to the powder the necessary energy for the creation of inhalable particles by disagglomeration. This aerosolisation of powders is, however, not or only insufficiently possible for the majority of patients because they are not able to inhale at such a high flow rate. To this adds that a high aerosol flow rate is inexpedient for the inhalational administration of medicaments because with such an application a substantial portion is deposited in the oropharyngeal cavity, particularly in the glottis, rather than arriving in the lungs.
Another problem involved in the inhalational administration of medicaments consists in the fact that the patients vary the volumes of inspiration, which gives also rise to a substantial variation of the medicament doses arriving in the lung. Such a variation of the volume of respiration occurs not only on one patient but is also subject to variations from patient to patient.
There is accordingly a strong need to provide a constant medicament dosage for inhalational administration at a low inhalation flow rate in order to achieve a selective effect depending on the site of application and the administered dose for the medicaments to be applied.
In accordance with the present invention this need is satisfied by a method of the type outlined by way of introduction, which consists of the steps of method defined in Patent Claim 1. In terms of the device a solution is provided by the features defined in Patent Claim 6.
Preferred further embodiments of the method or the device, respectively, can be derived from the respective dependent patent claims.
In the inventive method hence the provision of a closed container with mouthpiece is defined, which can be reduced in terms of volume and which receives a predetermined volume of a medicated aerosol quantity to be preferably inhaled in one breath, the compression of the elastic container in a direction towards the mouthpiece, the connection of a means for powder aerosol production to the mouthpiece, and the flow-controlled expansion of the elastic container for introducing air through the powder aerosol generator means for the purpose of producing the desired aerosol inside the container. The elastic container is surrounded by a closed compressible housing including an inlet valve for expansion and an outlet valve for a flow-throttled discharge of the preferably resilient container through the mouthpiece led out from the housing, with the container being expanded by application of a suction pressure in the housing.
In correspondence with a preferred embodiment of the invention the suction pressure in the housing is generated by external forces, preferably by at least one expansion spring engaging thereon. In an alternative, the suction pressure in the housing can also be created by the re-shaping elasticity of the housing, which is due to the material and which returns the housing into its uncompressed initial condition.
With the inventive method it is thus possible, with simple means without any additional electronic controller, to achieve a reliable provision of a predetermined constant medicament dose for inhalational administration, with the provided air-flow controlled compression during the inhalation as such contributing to the achievement of an effective slow inhalation.
In terms of the device the invention provides for one embodiment wherein a closed container reducible in terms of volume, a mouthpiece connected to the container, on which a powder aerosol generator can be connected for availability of the aerosol, a housing reducible in terms of volume, which surrounds the container on all sides and from which the mouthpiece is led out in sealed form, and means are provided for controlling the air inlet and outlet into or out from the zone between the container and the housing, with the housing being adapted to be changed from a volume compression condition into an envisaged availability condition for creating the envisaged aerosol volume in the container. On account of the inventive design hence a device is made available which is extraordinarily simple to produce and which is suitable for the inhalation at a small or low aerosol flow rate after separate aerosol production.
The means for air inlet and outlet control comprises two one-way valves which are preferably mounted at different locations with mutually counter-acting effect.
In correspondence with a preferred embodiment of the invention the housing is provided with separate means which may be used for expansion of the housing, with the separate means being preferably formed to include at least one externally engaging compression spring whilst the housing has an approximately cylindrical configuration with folding sections on the edge side.
In an alternative the housing may also consist of a resilient material which returns into its initial shape in the availability condition, instead of or in addition to the separate means.
The container in the housing consists preferably of a resilient material and has preferably a balloon-like shape. According to an improvement of the invention it may be fastened not only in the region of the mouthpiece but also in a region spaced therefrom on the inside of the housing so as to promote the latter""s inflation for the purpose of aerosol reception.
According to another expedient embodiment of the invention the housing is transparent at least partly for a check of the filling level of the container. With this provision the patient using the device can visually check the quantity of the filling and the aerosol quantity which is still available in the container during inhalation.
In correspondence with another embodiment of the invention the housing is provided with a releasable means for locking of the volume-compressed position, i. e. the position in which the housing and the container accommodated therein are most largely contracted in a direction towards the mouthpiece. On account of the releasable means, e. g. in the form of a biasing means, this so-called volume-compressed position can be used also for a ready-made condition of the device for selling purposes.
In accordance with the inventive device hence a biased housing is made available which is at least partly transparent and comprises a balloon-like container accommodated therein. Any system for powder aerosol production (DPI: Dry Powder Inhalator) can be easily mounted on the mouthpiece in an air-tight manner. When the housing is released from its volume-compressed position for the envisaged automatically occurring expansion the container, which is equally provided in the housing, unfolds under the effect of the generated subatmospheric pressure, with air being sucked through the powder aerosol inhaler into the balloon-type container for producing the aerosol in the desired dosage. In correspondence with a preferred further embodiment of the invention a so-called impaction separator may be provided in the mouthpiece, which retains aerosol particles of major size which have an aerodynamic diameter greater than 10 xcexcm because these particles cannot be inhaled anyhow.
After availability has been ensured the balloon-like container always contains a constant quantity of a predeterminable aerosol which is determined only by the powder aerosol inhaler, the air-flow controlled expansion of the housing and the design of the impaction separator. The device is extraordinarily simple to handle, even for unskilled persons, and after preparation of the aforedescribed availability the patient must only remove the powder aerosol inhaler from the mouthpiece, place his or her lips on the mouthpiece and discharge the balloon-type container in one breath. On account of the air flow control for the region between the housing and the container, which is implemented by a one-way valve, it is ensured that the patient can breathe only at an adjustable maximum flow rate; and due to this flow rate reduction and the limitation of the volume of the balloon-like container a patient inhales always the same aerosol quantity. A deposition in the extra-thoracic region is expediently minimized because the particles of major size are retained in the system already and because the flow rate is limited.
Due to the inventive embodiment of the method and the device the prerequisites are expediently created for an inhalational administration independently of a possible maximum inhalation flow rate of the individual patient, without any undesirable medicament remaining in the pharyngeal cavity for avoidance of extra-thoracic deposition, whilst it is ensured that the dose is constant because a patent inhales a constant volume and an upwardly limited flow. The device can be produced with extraordinarily small dimensions and at low manufacturing costs, with a compact folded condition being advantageous for distribution and transport. Electronic means are not required and only a small expenditure in terms of material is necessary; moreover, the device is suitable for unproblematic application with all dry powder inhalers so far licensed already.
With the new method and the new device hence a constant medicament dose can be expediently made available for inhalational administration at a low inhalation flow rate, which allows for a safe and reliable dimensioning of the volume for a specified range of application whereas dry powder inhalers so far known, which suffer from the shortcomings described by way of introduction, have been suitable for administration of only 2 to 10% of the active medicament substance in the correct dosage. Thus the inventive method and the inventive device serve at the same time to achieve a distinctly improved utilization of the medicaments as such so that the costs incurred by the treatment of patients over a major period of time are also reduced.
As far as the material of the device is concerned an antistatic material is envisaged for the container, which is permissible for use with medicaments, whereas the choice of materials for the housing is restricted only by the envisaged function on account of the absence of contact with the medicaments.